Sighting devices such as riflescopes have long been used in conjunction with weapons and firearms, such as rifles, handguns, and crossbows, to allow a shooter to accurately aim at a selected target. Because bullet and arrow trajectory, wind conditions, and distance to the target can vary depending upon shooting conditions, quality sighting devices typically provide compensation for variations in these conditions by allowing a shooter to make incremental adjustments to the optical characteristics or the aiming of the sighting device relative to the weapon surface on which it is mounted. These adjustments are known as elevation and windage adjustments, and are typically accomplished by lateral movement of an adjusting member, such as a reticle located within the riflescope, as shown in U.S. Pat. No. 3,058,391 of Leupold, or movement of one or more lenses within a housing of the riflescope, as shown in U.S. Pat. Nos. 3,297,389 and 4,408,842 of Gibson, and U.S. Pat. No. 7,827,723 of Zaderey et al.
The shooter typically makes such adjustments using rotatable adjustment knobs to actuate the adjustable member of the sighting device. Rotatable knobs may also be used to adjust other features of riflescopes, binoculars, spotting scopes, or other suitable optical devices, such as parallax, focus, illumination brightness, or other suitable features. Although the rotatable knobs are described in relation to use with sighting devices, rotatable knobs may be used to adjust an adjustable portion of other devices, and may include volume control knobs, channel selection knobs, radio station selection knobs, and other suitable knobs.
Automatically locking devices with rotatable adjustment knobs are known. For example, U.S. patent application Ser. No. 12/938,981 filed Nov. 3, 2010 and published as US 2011/0100152 A1, which is incorporated herein by reference describes an automatically locking adjustment device. The locking device includes a rotatable knob with two buttons on opposite sides of the knob that must be squeezed together to unlock the knob for rotation and thereby enable a desired adjustment. When the buttons are released, the knob is immediately locked at its current rotational position. One drawback of this adjustment device is its relative complexity and attendant expense of manufacture. The squeezing pressure required to unlock the knob for rotation may also make it more difficult to effect multiple fine rotation adjustments in the course of an aiming operation, when inadvertent rotation of the knob is less of a concern.
The present inventor has, thus, recognized a need for an improved locking adjustment mechanism for preventing inadvertent adjustment of an optical or electrical setting of a device.